Virginia State Del. Owen B. Pickett today released his delegates to the Democratic Party's nominating convention, raising the possibility of a wide-open battle in the race to succeed retiring U.S. Sen. Harry F. Byrd Jr.

Democratic leaders immediately praised Pickett, a little-known state legislator handpicked as a candidate by Gov. Charles S. Robb and other party officials, for what they called his bold move throwing open the convention and challenging his critics to jump into the race.

Pickett's most vocal critic, state Sen. L. Douglas Wilder (D-Richmnd), refused to accept the offer. Wilder, the state's top black elected officeholder who has been threatening his own independent Senate candidacy, said he had no plans to challenge Pickett for the Democratic nomination because the Virginia Beach legislator has already enough delegates to guarantee the nomination.

"It's a total empty gesture," said Wilder. "How can you release delegates to a convention when those delegates still want you to be nominated? Even Ray Charles could see through this one."

Many party officials around the state said that Pickett's move would invigorate the campaign but should not seriously endanger his chances for nomination at the party convention in Roanoke June 4 and 5. During a series of sparsely attended meetings this month, Pickett's forces captured 1,914 convention delegates, 164 more than needed for the nomination. Although the Pickett delegates are now free to vote for someone else, the party officials said they believed only the entry of a strong, new candidate would produce defections from Pickett.

In Fairfax County, for example, where grumblings about the conservative Pickett have been widespread, party chairman Dottie Schick said she had been talking to delegates all day and "We're all holding tight for Owen . . . I don't expect any mass exodus."

Nevertheless, Pickett's public invitation for others to "challenge me on the issues" was tantalizing enough to two leading Democrats--state Senate Majority leader Hunter B. Andrews (D-Hampton) and Fairfax County Commonwealth's Attorney Robert F. Horan--to cause them to reassess their plans.

"This certainly changes the ball game quite a bit," said Horan, a veteran prosecutor who had ruled himself out as a Senate candidate earlier this year. "An open convention offers some possibilities. It demands another look."

Speaking from his Hampton law office, Andrews said he was interested in becoming a candidate but added: "I want to counsel with my friends and seek some guidance."

The key to opening the convention, several Democrats said, would be whether Robb backs off his earlier endorsement of Pickett. There were no signs of that today. Robb, who consulted with Pickett before his press conference, issued a statement applauding the candidate's "excellent move. It won't solve all the problems, but it is a good first step."

Pickett's problems as a candidate began almost from the day this winter when Robb and other party leaders emerged from a series of closed-door meetings and spread the word that the obscure state delegate was their choice to oppose the Republican party's expected candidate, Rep. Paul S. Trible of Newport News. A 51-year-old Virginia Beach lawyer and certified public accountant, Pickett was selected as the compromise choice because, the party leaders said, he was the candidate with the "least negatives."

Others have said privately, however, that Pickett's blandness also meant that he was the candidate with the "least positives." Until recently, most critics concentrated their fire on the process by which he was picked, a method they alleged was reminiscent of the backroom politics of the old Byrd organization.

"It was a bad process--the idea of selecting somebody outside of the convention," said Horan, who didn't participate in the closed-door meetings of potential candidates. "I thought it was the non-Democratic way to go."

As discontent with Pickett spread and the threat of Wilder's independent candidacy mounted, party leaders began pressuring Pickett to take a dramatic step that would demonstrate he was not hand-picked by party bosses. Among those who said today they had urged this course on Pickett was state party chairman Alan Diamondstein.

"The process ought to be open," Pickett said at today's press conference. "I'm willing to take my chances."

The candidate also responded to criticism that his bland personality would be a liability in a statewide campaign against Trible, the photogenic young congressman who is expected to be the Republican nominee.

"I think the public is interested in someone who is competent, who is knowledgeable," he said. "While I might not be best entertainer on the circuit, I think I'm the best one to represent Virginia in the U.S. Senate."

Despite initial assessments that releasing the delegates would not change the probable outcome, some party leaders lavished praise on the legislator. "It's a gutsy move," said lobbyist William G. Thomas, a former state party chairman and a key participant in the meetings that lead to Pickett's selection. "Here's a guy who's got all the cards and he's saying, 'I'm willing to throw them all back in and replay the game.' I think it will be good for the party."